Enabling this makes balance --flat --empty also show parent accounts without postings,
in addition to those with postings and a zero balance. Disabling it shows only the latter.
No longer supported, but leave this here for a bit.
flatShowsPostinglessAccounts = True

Generate a simple balance report, containing the matched accounts and
their balances (change of balance) during the specified period.
This is like periodBalanceReport with a single column (but more mature,
eg this can do hierarchical display).